Ancient Life in Kansas Rocks, part 22 of 27
In this photo are two teeth from the ray Ptychodus (slightly enlarged). The uppermost is a view of the surface of the tooth, the other a side view. Note that they are low and rounded with shallow ridges much like a grinding wheel and have no sharp cutting edges. Ptychodus had up to 600 teeth is each jaw, arranged in parallel rows forming a continuous pavement. These teeth reveal that the fish lived on or near the bottom, and were adapted to gathering and crushing crabs and oysters.
In contrast, Corax, right, and Lamna, left, were active predaceous sharks as revealed by these sharp cutting and tearing teeth. Lamna had 300 or more large, pointed teeth, some of which had accessory cusps, as pictured here. Shark's teeth commonly weather out of the enclosing rock, such as the chalk in western Kansas, and lie about on the surface as though suddenly deposited by some great flood. No recent flood accounted for these fossils, for the rocks from which these teeth have weathered are about 75 million years old! (Greenhorn Limestone, Upper Cretaceous)
Kansas Geological Survey
Placed online Feb. 1997
URL = "http://www.kgs.ku.edu/Publications/ancient/f22_sharks.html"
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